The disclosure relates generally to fluid piping members. More particularly, the disclosure relates to the field of connections between lengths of pipe or between pipes and fittings.
The construction of pipelines generally involves the axial connection of two lengths of pipe to form a single pipeline conduit for transporting materials from one point to another. Along the pipeline, one or more fittings may join the pipe pieces to other components in the pipeline. Due to the nature of the materials usually conveyed via pipelines, pipeline conduits, joints between axially-joined pieces of pipe, and joints between pipes and fittings need to be substantially leak-proof.
Another important design requirement exists when it becomes necessary to join the pipe components in a restrained manner. This is usually desired in order to prevent the pipe components from separating due to thrust forces that often occur when the pipeline is subjected to internal pressure or when earth tremors or other external events occur. As such, the overall reliability of the piping system often depends on the stability of the couplings used throughout the system. Accordingly, the pipe industry has focused some attention on the problem of maintaining connections between adjacent lengths of pipe after installation. As a result, several attempted solutions and approaches are known in the art. Accordingly, a number of different arrangements have been developed in an attempt to provide secure couplings between pipe ends. It is known to employ gripping members in order to prevent uncoupling of pipe joints by longitudinal forces imposed on coupled pipe sections. Other arrangements include combinations of rings and seals that use compression-type connections to hold pipe systems together. For example, a gland and gripping ring may be used in combination to position, compress, and seal a gasket on a pipe.
References to “pipe” with respect to the application or use of embodiments of the present disclosure shall be understood to include fittings, connections, and any other appurtenances to pipes.
While the degree of pipe restraint on a coupled joint can be important, it can be equally important that an adequate gasket compression be achieved to ensure a correct seal against leaks in the piping system. Accordingly, typical bolt-type couplings having a gasket to effect sealing and a lock ring to restrain the coupled pipe against pull-out are common in the prior art. In these couplings, a gripping ring is imposed on the pipe, between the lock ring and the gasket, to operationally grip the pipe prior to or simultaneous with compression of the gasket. One drawback of such couplings, however, is that they can result in an undetectable but inadequate gasket seal because the gripping ring often engages the pipe and locks it into place before the seal is properly actuated.
Accordingly, other compression couplings have been designed with various arrangements and parts to prevent gripping ring lock-up prior to compression of the sealing gasket. For example, U.S. Pat. No. 4,070,046 to Felker et al. discloses pipe couplings for both restraining and sealing the pipe ends. One major disadvantage of this design, however, is the timing of the gripping and sealing members' actuation. Because the gripping members engage the pipe ends at very low torque, the follower member becomes locked onto the pipe end with this design. Accordingly, proper gasket compression can only be achieved by ensuring that there is a gap between the pipe ends and that at least one of the pipes is free to move axially into the coupling. These requirements make this design unsuitable for use in certain applications where such pipe movement is not possible. Another problem with this design is that gasket compression may be reduced when the coupled pipe is under an axial tension load because the gripping member supporting the gasket has a tendency to move away from the gasket.
U.S. Pat. No. 4,569,542 to Anderson et al. discloses a bolt-type coupling designed to provide clearance functions, so that gasket compression is achieved before the gripping ring effectively grips the pipe and locks the coupling in place when the bolt fasteners are tightened. U.S. Pat. No. 5,803,513 to Richardson discloses the use of a plurality of skid pads strategically placed over the teeth of the gripping ring to prevent it from prematurely engaging the pipe before compressing the accompanying gasket. However, while the couplings disclosed by U.S. Pat. Nos. 4,569,542 and 5,803,513 are useful for their intended purpose, they require additional or complicated arrangements of parts, which may increase cost and/or hinder the ease of coupling installation.
Another partial solution to these problems is proposed in U.S. Pat. No. 4,606,565 to Royston, which provides separate follower members for the gripping and the sealing members. With such a coupling, complete and repeatable gasket compression, as well as complete and repeatable gripping engagement, are possible regardless of installation conditions. While such a coupling solves the problems of gasket compression and gripping engagement, the design requires assembly of a number of pieces and proper tightening of twice as many bolts. Accordingly, the solution proposed in U.S. Pat. No. 4,606,565 overcomes the limitations of the other designs, but, the design increases the number of pieces and causes the installation of the device onto the pipe to be cumbersome and overly time consuming.
Yet another solution to these problems has been described in U.S. Pat. No. 7,004,511 to Barron et al. in which an intermediate ring, located between a sealing gasket and a gripping ring, has a restraining member adapted for restraining the gripping ring to prevent the gripping members from gripping a male piping member until after the sealing gasket is compressed into sealing engagement with the male piping member and a female piping member.
However, the reliability of the sealing arrangement between the female piping member, sealing gasket, and male piping member depends on a uniform distribution of a force compressing the sealing gasket especially in the long term. In order to achieve uniform force distribution, concentric location of the female piping member, male piping member, and coupling device element that compress the sealing gasket is desirable. The prior art does not offer a solution to this problem.
There remains a need for an improved pipe coupling that provides a desired degree of sealing and gripping functions regardless of installation conditions, that is simple to install and manufacture, and that retains an appropriate seal over time. It is to such a pipe coupling that various embodiments of the present disclosure are primarily directed.